SEATTLE -- Breanna Stewart, this season's MVP, and Elena Delle Donne, the 2015 MVP, will indisputably be the best players on the court when the Seattle Storm and Washington Mystics meet in the WNBA Finals, which open Friday in Game 1 at KeyArena (ESPNews, 9 p.m. ET).

However, Seattle shooting guard Jewell Loyd might just be the most important player in this series.

"In some ways, it could be a series where (Delle Donne and Stewart) negate each other and now it's all the other matchups that make the difference in the series," Washington coach Mike Thibault said. "Historically, sometimes when you have two great players like that and they're both scoring 20-some points per game, the difference is going to come somewhere else."

The most likely candidate is Loyd, one of the Storm's three 2018 All-Stars (Stewart and veteran Sue Bird are the others) and the team's bellwether throughout the season. Seattle went 10-0 during the regular season when Loyd scored at least 20 points, as compared to 16-8 in all other games.

The Storm reached the Finals without a strong performance from Loyd, who combined for just 32 points on 9-of-36 shooting over the last four games of Seattle's five-game semifinal win over the Phoenix Mercury and watched the fourth quarter of Game 5 from the bench. Winning this series will likely require Loyd to get going. Thibault's team aims to stop that.

"We've made it a priority that (Jewell's) got to feel uncomfortable as best as we can," Thibault said. "We put one of our best defenders on her every game and try to slow her down a little bit. Her athleticism is so good that she can explode and go off at any time, but she's a priority."

The Mystics were once derisively referred to as "the mistakes." But no more. Elena Delle Donne and Washington are headed to their first WNBA Finals.

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Phoenix had the same priority against Loyd, who has historically been difficult for the Mercury to stop -- until they utilized ace defender Briann January, a six-time WNBA All-Defensive Team pick who missed out on a spot this year but got a vote from Storm coach Dan Hughes.

"It seemed that Jewell torched Phoenix in the regular season -- I think she averaged like 30, I wouldn't be surprised -- and did really well in Game 1," Bird said. "So they made an adjustment by putting arguably the best on-ball defender from a guard standpoint on her in Briann January. That was tough for Jewell, and that's OK. It's OK to get stifled a little bit. But I definitely want to see Jewell bounce back. I know she wants to bounce back and this series starts a whole new ballgame for Jewell. She can shake off the semis and just move on."

Echoed Loyd: "It's definitely important, something I'm focusing on. It's also good to know that you have great teammates and no matter what, if your shot's going in or not, they come in and help you out."

Sami Whitcomb was that teammate during Tuesday's Game 5 against Phoenix. Unlike Loyd, the No. 1 pick after her junior year at Notre Dame, Whitcomb went undrafted out of the nearby University of Washington. It wasn't until seven years after her college career that Whitcomb's star turn in the Australian WNBL earned her an invitation to training camp from the Storm last season, and she made her WNBA debut at age 28.

With Seattle in urgent need of the energy and shooting Whitcomb brings off the bench, she found herself in a key role after not seeing any action during the first two games of the series. Whitcomb played the final 14:39 of Game 5 as the Storm outscored the Mercury 45-27 to come back and win.

"It's sort of the moment you prepare for when you're in a gym and you're playing make-believe in your head," Whitcomb said. "You try to stay prepared, you try to stay ready and when you come in you just want to bring that spark and that energy. It was just really nice to feel like I was making an impact, feel like I was helping the group."

Whitcomb's contributions didn't surprise Loyd.

"That's the Sami that we all know," Loyd said. "She's been doing that all year for us. She's here two hours before practice either running a mile or getting shots up. So I had all the confidence in her that she was going to come in and capitalize on her moment.

"That's kind of been our conversation. I talked to Sami before the series and encouraged her to just be ready. We knew we were going to need our bench and she stepped up and I was so happy for her."

Sami Whitcomb played the final 14:39 of Game 5 on Sunday and scored six points as the Storm outscored the Mercury 45-27 to rally for the win. Barry Gossage/NBAE via Getty Images

After the game, Storm coach Dan Hughes shared that during the fourth quarter he'd gone to Loyd on the bench and told her to stay ready for when she came back in. Loyd responded, "No, Sami is going, you let her go, Coach." That selflessness moved Hughes.

"She was all about the team," Hughes said. "That was the moment that I knew that we were going to find success, when the totality of what you're doing is greater than your own place."

From Whitcomb's perspective, Loyd's support went far beyond just advising Hughes to keep the backup on the court.

"During all that game, I don't know if you would have seen it, but we're coming off [and] every time she's hyping me in timeouts, she's saying, 'Stay with it,'" Whitcomb recalled. "There's no sulking, nothing's about her. In those moments, honestly, that gives me even more confidence to know that someone like Jewell -- a superstar in this league -- believes in me enough to just support me and say something like that."

As impressed as her Seattle teammates and coaches were by her response to sitting during Game 5, they want to see Loyd back on the court and scoring efficiently during the WNBA Finals. Despite primarily being defended by bigger Mystics wing Natasha Cloud, who is 2 inches taller, Loyd averaged 17.0 PPG on 19-of-37 shooting in three regular-season matchups against Washington, two of them won by the Storm. A performance closer to that than her down semifinals could make the difference in Seattle winning this series and the championship.

"I think it's just important in every game to get Jewell going," Hughes said. "... She's such a big part of us that getting her in rhythm is just another weapon that's important to us. But she'll be fine."